Evaluation Of Two Mg2+-Selective Electrodes By Means Of A Flow-Through Device

Monitoring the ionized magnesium (Mg2+) concentration in critically ill patients can prevent development of serious and potentially fatal complications. The analyzers KONE Microlyte 6 (KONE Instruments, Espoo, Finland) and NOVA CRT (NOVA Biomedical, Waltham, MA, USA) provide the discontinuous measurement of Mg2+ and were evaluated in several studies. It was our objective to integrate the Mg2+-selective electrodes into a device for continuous online measurements. This device is suitable not only for research but also for a specific evaluation of electrode characteristics. It allowed us to compare the genuine electrodes and reference systems independently of their specific analyzers. Precision, accuracy, response time, limit of detection, drift and interferences were assessed by continuous flowthrough measurements and discussed in comparison to the results of previous studies. The NOVA electrode proved to be superior regarding accuracy, sensitivity and selectivity, especially with respect to calcium. It was demonstrated that current commercial serumlike control materials were not appropriate for quality control of the assessed Mg2+-electrodes. However, despite the fact that the electrodes are commercially used for discontinuous measurements, both sensor types can be used for continuous online measurements in an extracorporeal circulation in a rat model. The NOVA electrode showed superior characteristics with this application as well. This study should also be understood as a contribution to the development of devices for online analyzers used in pointofcaretesting.